Keep project config and checked-in workflows under .fabro so they stay out of
normal repo listings. Update config discovery, CLI project commands, fixtures,
docs, and checked-in workflow paths to use .fabro/project.toml and
.fabro/workflows/*.
Replace the unsupported Bun.watch call in the SPA build script with
node:fs.watch so `bun run dev` keeps running in local development.
Add a regression test that verifies watch mode stays alive until
interrupted.
Replace the old React Router SSR setup with a static SPA build served by
fabro-server, move setup and GitHub auth handling into Rust, and update the
default local web URL and stale Arc-era references to match the Fabro name.
